1. Field of the Invention
The present invention relates to systems for pressure isolation of one or more tools adapted for use in a wellbore.
2. Description of the Related Art
Hydrocarbons such as oil and gas are recovered from a subterranean formation using a wellbore drilled into the formation. A number of tools are used throughout the process of drilling and completing the wellbore and also during the production life of the well. Many of these tools are energized using pressurized fluid that is self-contained in the tool, pumped downhole from the surface, or fluid that is produced from the well itself. These tools, which are sometimes referred to as hydraulically actuated tools, can be put to a number of uses.
One use for hydraulically actuated tools is to set a liner hanger. During drilling, the wellbore is lined with a string of casing that is cemented in place to provide hydraulic isolation and wellbore integrity. The liner hanger is used to hang or anchor a liner off of a string of other casing string. Several types of liner hangers are known in the art, which includes hydraulic liner hangers. In conventional hydraulic liner hangers, fluid is supplied under pressure into an annular space between a mandrel and a surrounding cylinder. The hydrostatic pressure of the fluid between the cylinder and the mandrel creates a force on the inner surface area of the cylinder that causes the cylinder to slide longitudinally. Hydraulically actuated liner hangers are illustrative of wellbore tools that utilize an applied fluid pressure for operation.
Because conventional hydraulically actuated wellbore tools, such as liner hangers, utilize relatively high fluid pressure for activation, these tools can be vulnerable to high fluid pressures occurring after setting or activation. For instance, during pressure testing of a liner hanger assembly, the relatively high test pressures can rupture seals between a cylinder and mandrel or even deform the relatively thin mandrel. Typically, expensive seals and costly materials are used in these wellbore tools to reduce the risk of failure do to exposure to high post-activation pressures.
The present invention addresses these and other drawbacks of the prior art.